24 BULLETIN 183, U. S. DEPARTMENT OF AGRICULTURE. 



Manchuria and Oderbrucker barleys, the nature of the secreting sur- 

 face is of importance. 



As the size of the grain increases, the efficiency of the converting 

 power becomes a vital question. The relative decrease of the sur- 

 face of the epithehal layer, together with the increased percentage 

 of starch in the endosperm, makes an adequate amount of diastase 

 of the utmost importance, especially if it be desired to convert 

 starch in addition to that already in the endosperm. To have the 

 largest contact area, the embryo must completely occupy the prox- 

 imal end of the grain, and the grain itself must be as broadly oval 

 as possible in order to provide for this maximum expansion. When 

 these conditions are fulfilled, the resulting scutellum is a broad organ, 

 reaching well over the shoulders of the grain and resting in a shallow, 

 saucer-shaped depression in the endosperm. 



To test the accuracy of this conclusion, examinations have been 

 made of almost every commercial barley in the world. Several of 

 the types foimd are shown in Plate V, figure 2, and in Plates VI and 

 VII. In all cases where the grains were large, the varieties recog- 

 nized as superior malting barleys each possessed a scutellum of the 

 above type. On the other hand, barleys known to be inferior for 

 malting were invariably characterized by the other extreme of 

 scutellum, that is, by one which did not reach out over the shoulder 

 of the grain. Usually a sUght compensation for defective breadth 

 of scutellum was offered by its being deeply smiken in the endosperm. 

 This addition of surface was sHght, as it must be readily reahzed that 

 the increase of the few degrees of surface secured could not offset the 

 very considerable decrease of diameter. The comparative area of 

 the spherical surface of the large scutellum is actually greater than 

 that of the sUghtly elongated, small one, so that the broad, flat type 

 of necessity presents the greater secretmg surface. 



There seems to be a more or less definite correlation between the 

 shape of the scutellum and the form of the grain. A long, pointed 

 grain is almost invariably accompanied by a narrow, deeply sunken 

 scutellum. Of course, the fact that the proximal end was reduced 

 would of necessity cause a hke reduction of the embryo. However, 

 even more than such inevitable restriction usually occurs. In such 

 grains the borders of the scutellum in a moistened grain do not ordi- 

 narily protrude at the points of contact with the aleurone layer, but 

 are even more narrow than the available space requires. In a very 

 few types, as the Smyrna, this is not wholly true. 



Wliile the most important factor of enzymatic production is thus 

 seen to be the surface area of the secreting organ, there is still an 

 additional element. There may be a difference in the quality of the 

 secreting tissue. In other words, the epithehal layer varies with 

 reference to the character of its cells. In some barleys it is made up 

 of short, broad cells; in others the units are long and narrow. (See 



